1. Field of the Invention
The invention relates to a portable electric cutting apparatus of a portable circular saw, a portable jig saw, etc., having a fan for cooling an electric motor.
2. Description of the Related Art
FIGS. 12 and 13 show the configuration of a portable circular saw as an example of a portable electric cutting apparatus in a related art.
FIG. 12 is a broken plan view of a portable circular saw in a related art and FIG. 13 is a bottom perspective view of the portable circular saw on the rear thereof. The portable circular saw shown in the figures includes a saw blade 1, an electric motor 2 for rotating the saw blade 1, a motor housing 3 for housing the electric motor 2, a saw cover 4 for holding the saw blade 1 for rotation, and a base 5 placed below the motor housing 3 and the saw cover 4 and having an opening 5a for allowing the saw blade 1 to project from the lower face. The saw cover 4 is attached to the motor housing 3 and the base 5 is joined to the saw cover 4. A safety cover 6 having a shape covering the outer peripheral portion of the roughly semicircle part of the saw blade 1 is held on the saw cover 4 so as to be able to rotate concentrically with the saw blade 1.
The power of the electric motor 2 is transferred to the saw blade 1 via a gear (not shown), etc., and the saw blade 1 is rotated at predetermined speed. A fan 7 for cooling the electric motor 2 is attached to the electric motor 2. When the electric motor 2 is driven, the fan 7 rotates and fan wind 9 flowing into the inside of the motor housing 3 from a suction port 8 provided at the end part of the motor housing 3 on the opposite side to the saw cover 4 flows through the inside of the motor housing 3 for cooling the electric motor 2.
By the way, a wall placed between a saw blade housing part 4a of the saw cover 4 and the motor housing 3 is provided with a plurality of partition walls 4b forming a fan wind discharge port, and each of the partition walls 4b is provided with a slope part 4c of a shape to incline to the front in the cutting direction as it is toward the side end face of the saw blade 1.
The fan wind 9 flowing through the inside of the motor housing 3 passes through the partition walls 4b provided with the slope parts 4c, is discharged into the saw blade housing part 4a, is sprayed slantingly on the side of the saw blade 1 or the side of the safety cover 6, and is discharged toward the front of the opening 5a of the saw blade housing part 4a in the cutting direction with little changing the discharge direction to the front in the cutting direction.
As shown in FIG. 13, a groove part 5b communicating with the opening 5a is provided from the opening 5a to the end part of the base 5 on the bottom of the base 5, in the front portion of the opening 5a in the cutting direction. As shown in the figure, a guide piece 10 having a guide part 10a for pointing to the cutting edge of the saw blade 1 is provided at the front end part of the base 5 in the cutting direction. The guide piece 10 has a bottom positioned above the bottom of the base 5.
The groove part 5b is provided on the extension in the length direction of the saw blade 1 and has a dimension in the width direction set larger than the width dimension of the saw blade 1.
By the way, the fan wind 9 discharged into the range of the opening 5a by the slope parts 4c of the saw cover 4 blows against the top of a cut material positioned in the range of the opening 5a at the cutting work time and is diffused. The groove part 5b is provided on the bottom of the base 5 as described above, whereby the discharge direction is determined so that a part of the diffused fan wind 9 passes through the space between the groove part 5b and the top face of the cut material and is discharged along the top face of the cut material, and the wind is discharged into the front side in the cutting direction rather than the end part of the base 5. The fan wind 9 flowing out into the groove 5b passes through below the guide piece 10 and is discharged into the front side in the cutting direction rather than the end part of the base 5. The fan wind 9 makes it possible to remove chips accumulated on the mark-off line on the front side in the cutting direction rather than the end part of the base 5, so that it is made possible to easily check the correlation between the guide part 10a of the guide piece 10 and the mark-off line.
In cutting work using the portable circular saw, often a mark-off line is drawn on the top face of a cut material and cutting work is executed while the guide part 10a is matched with the mark-off line to improve the cutting accuracy and therefore making it possible to easily check the correlation between the guide part 10a and the mark-off line leads to improvement in workability. (Please see JP-A-2002-307696.)